We have referred to the ENT to get to the root of the problem especially if they are young. Sleeping with their mouth open allows for the tongue to not lie on the floor of the mouth which may affect growth of the jaw and cause improper bite. Also possible sleep apnea in the future. In the interm I send them home with MI paste and/or Biotine products.
I usually recommend 3-4 month recare depending on the patient, as well as an rx paste like MI paste or prevident and of course an electric toothbrush. If the patient is also taking medications and report xerostomia during the day I may include a biotene rinse.
I recommend protecting the tissue with a little Vaseline before going to bed in addition to all the recommendations given by Avalene R.D.H
Mouth rinses before bed can help. Biotene has a great one that helps to coat the tissues and keep them protected.
If they are young, I try to teach correct mouth posture. Tell parents to remind them to close their lips and breath through their nose, teeth close but not clenching, and tongue at the roof the mouth right behind centrals.